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Ultracold Quantum Gases Group

Welcome to the ultracold quantum gas research group at Aarhus University!

In our research we investigate the properties of atomic gases at extremely low temperatures. This allows us to understand the fundamental quantum mechanical behaviour of these many particle systems.


Left: 39K. Right: 87Rb

First dual condensate in MIX lab

The first heteronuclear 39K-87Rb BEC-Mixtures were produced in the MIX laboratory on the 12th of May. The inter-species tunablility of the scattering length between 39K-87Rb allows for a wide range of exciting experiments including fundamental investigations of interactions in heteronuclear many particle quantum systems, molecular quantum gasses, and the simulation of the impurity problem under changing interactions. Currently, both condensates have around 104 atoms. (05/2014)

Time limited optimal dynamics beyond the Quantum Speed Limit

The quantum speed limit sets the minimum time required to transfer a quantum system completely into a given target state. At shorter times the higher operation speed has to be paid with a loss of fidelity. Here we quantify the trade-off between the fidelity and the duration in a system driven by a time-varying control and interpret the result in Hilbert space geometry. Formulating a necessary convergence criterion for Optimal Control (OC) algorithms allows us to implement an algorithm which minimizes the process duration while obtaining a predefined fidelity. http://arxiv.org/abs/1405.6079 (05/2014)

Spin dynamics in a two dimensional quantum gas

Published in Physical Review A, Rapid comm.!

We have investigated spin dynamics in a 2D quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimposed  angular density modulations. The  density distributions depend on the applied magnetic field and are well explained by a simple Bogoliubov model. We  show that the two clouds are anti-correlated in momentum space. The observed momentum correlations pave the way towards the creation of an atom source with non-local Einstein-Podolsky-Rosen entanglement. (05/2014)

One- and two-qubit quantum gates using superimposed optical-lattice potentials

Published in Physical Review A!

We propose an architecture which allows for the merger of a selected qubit pair in a long-periodicity superlattice structure consisting of two optical lattices with close-lying periodicity. We numerically optimize the gate time and fidelity, including the effects on neighboring atoms and in the presence of experimental sources of error. Furthermore, the superlattice architecture induces a differential hyperfine shift, allowing for single-qubit gates. The fastest possible single-qubit gate times, given a maximal tolerable rotation error on the remaining atoms at various values of the lattice wavelengths, are identified. (03/2014)

Congratulations to Nils!

On the 31st of January, Nils Winter defended his PhD thesis "Creation of 39K Bose-Einstein condensates with tunable interaction". The assessment committee consisted of Professor Gerhard Birkl from the Technical University of Darmstadt and Professeor Henning Moritz from the University of Hamburg. Nils is continuing in the group as a post-doctoral researcher. (01/2014)

Congratulations to Romain!

On the 23rd of January Romain Müller succesfully defended his progress report "Towards a high-resolution, non-destructive imaging experiment". (01/2014)

First BEC in HiRes labs

The first Bose-Einstein condensate in the HiRes experiment was obtained on Tuesday the 21st of January. The HiRes experiment is aiming at investigating cold gases in optical lattices using high optical resolution. More information here. (01/2014)

New national laser centre: DANLASE

A new national laser centre has been initiated by the Danish Ministry of Science, Innovation and Higher Education. One of the centre's objectives is to promote laser knowledge to industrial and research partners. DANLASE (Danish National Laser Centre) is an interdisciplinary centre with close collaboration between Aarhus University (AU) and the Technical University of Denmark (DTU). We will be part of this centre, with particular emphasis on high precision frequency measurements. Read the news announcement here. (01/2014)

Lundbeck Foundation Fellowship to Jacob Sherson

Jacob Sherson has just been awarded a Lundbeck Foundation Fellowship valued at DKK 10 million. See more details on the official news announcement.   (11/2013)

Spontaneous symmetry breaking in spinor Bose-Einstein condensates

Published in Physical Review A!

Within this paper we present an analytical model for the theoretical analysis of spin dynamics and spontaneous symmetry breaking in a spinor Bose-Einstein condensate. This allows for an intuitive understanding of the processes and provides good quantitative agreement with earlier experiments. One main result is that the dynamics of a spinor BEC can be understood by approximating the effective trapping potential with a cylindrical box. The resonances in the creation efficiency of the atom pairs can thus be traced back to excitation modes of this confinement. This allows for a characterization of the symmetry-breaking mechanism, showing how a twofold spontaneous breaking of spatial and spin symmetry can occur. (11/2013)

Congratulations to Lars!

On the 19th of November, Lars Wacker defended his progress report "Production of 39K and 41K Bose-Einstein Condensates". (11/2013)


Our research is supported by:

The Danish National Research Foundation within the Center for Quantum Optics (QUANTOP).

Henvendelse om denne sides indhold: 
Revideret 09.10.2014

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Institut for Fysik og Astronomi
Aarhus Universitet
Ny Munkegade 120
8000 Aarhus C

E-mail: phys@au.dk
Tlf: 8715 0000 (Aarhus Universitets hovednummer)
Fax: 8612 0740

Medarbejdere, studerende, ledelse

Nyttige numre

CVR-nr: 31119103

Momsnummer/VAT: DK 3111 9103
(alle internationale køb)

P-nr: 1009828059

EAN-nr: 5798000419872

Stedkode: 2902

Enhedsnummer: 5200

Aarhus Universitet
Nordre Ringgade 1
8000 Aarhus C

E-mail: au@au.dk
Tlf: 8715 0000
Fax: 8715 0201

CVR-nr: 31119103
EAN-numre: www.au.dk/eannumre

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